The present invention relates to a switch construction and, more particularly, to a grounding switch for earthing a charge stored on a power transmitting line circuit.
Generally, a grounding switch includes a resistance contact unit, a short circuiting contact unit, and a resistor connected in parallel with the short circuiting contact unit. The parallel circuit of the short circuiting contact unit and the resistor is constructed in series with a resistance contact unit.
In grounding switches of the aforementioned type, in advance of a grounding of the power transmission line circuit, the resistance contact unit is first closed so as to ground the power circuit through the resistor, and then the short circuiting contact unit is closed to short circuit the resistor and to ground the power circuit. The reason the power circuit is grounded through the resistor stems from the fact that, if any residual charge remains on the power circuit, the circuit suffers a dielectric breakdown by a switching surge.
In previously proposed grounding switch constructions, the resistance contact unit and the short circuiting contact unit are arranged on the same axis so that an axial length of the sheath or casing accommodating the units is relatively long. Additionally, in the proposed grounding switch units, another sheath or casing must be provided to accommodate the resistor thereby complicating the construction of the grounding switch as well as increasing the overall total cost thereof.